IRIG 106-86 Chapter 8 describes the standard for acquisition of MIL-STD-1553 traffic flow. All incoming words (command, status, or data) are transmitted and fill words are used to maintain continuous data output. If all incoming words are not needed, or if other data such as sampled analog data from transducers are also to be transmitted, then a different approach is warranted. Selected data from the avionics bus can be placed into predefined PCM words, eliminating the transmission of useless data, and optimizing the bandwidth available to a Class I telemetry system. The engineering considerations and constraints for avionics bus data acquisition and analysis will be explored in this paper.

This paper gives detailed ideas and methods about the design and development of high performance MIL-STD-1773 airborne fiber optic data bus. To reject impulsive interference efficaciously, the large core and large numerical aperture fiber optics are adopted, as well as high- emitted power LEDs and a low noise optical receiver structure to get high signal-to-noise ratio at decision time. Two new modulation technique----digital frequency shift keying and partial tri-level Manchester are recommended, which are very attractive in the design of modern optical bus. Meanwhile, VLSI chips COM1553B are used to construct bus control interface unit, thus many advantages have been brought out.

MIL-STD-1553 multiplex data buses are commonly used to link complex software-controlled systems in modern aircraft. The software in these aircraft is routinely updated; each update requires flight testing. Also, sophisticated weapons and electronic warfare systems which are integrated into operationally-ready aircraft must be routinely evaluated. The simplest way to perform the required evaluation is to record all the data from the multiplex data buses during an operational flight; these data can then be replayed and examined after the flight. Traditionally, some operational systems had to be disabled or removed from an aircraft to allow installation of a data acquisition system. This paper discusses a MILSTD- 1553 multiplex bus Record-All Small Data Acquisition System (RASDAS) installed in a McDonnell Douglas CF-188 fighter aircraft to record all data from two 1553 multiplex data buses without displacing any operational equipment. The specific requirements and constraints associated with evaluating the integrated systems of a CF-188 aircraft are examined; further, RASDAS implementation in this aircraft type is discussed from planning to flight evaluation.

Research and development testing of rotating machinery has always been limited in the number of measurements because slip ring assemblies have a limited number of conductors available for signals to pass from rotating to non rotating sections. Such testing has been impeded because relatively long wires are needed to pass low level analog signals. Because of the line resistance and capacitance and their susceptibility to stray fields, much effort is dedicated to the investigation of line loss and protection from EMI. The solution in recent years is to use current drivers or to digitize these signals as close to the transducers as possible or to employ painstaking procedures for correction of data in software. At NASA's Ames Research Center, recent research requirements have approached the limit of practical slip ring assemblies. Line lengths needed for wind tunnel tests can be 300 feet. The solution provides for an increase of channels by an order of magnitude, improved data quality, elimination of all efforts to correct data for line loss, a simple and quick installation, real time monitoring with extensive graphics capability and a manageable method for data storage. The system is called the Rotor Mounted Data Acquisition System (RMDAS) and has been acquired through a U.S. Government contract with Aydin Vector Division in Newtown, Pennsylvania. This is a high density, high speed, signal conditioning and multiplexing system which mounts on the rotating hub of full scale rotorcraft and transmits PCM, NRZ-L bit streams to a fixed end data system. The system is 512 channel capable at 20 KSPS/channel when configured for maximum channel capacity. The channel sampling capability for a single channel or for a group of channels is 177 KSPS. The individual channel sample rate can be changed by reprogramming the number of channels per segment. Various other configurations exist but always with an aggregate rate of 17 Mbps, including overhead words, per serial bit stream. This system utilizes 12-bit digitizers to provide high accuracy over the operating temperature range.

The Boeing Commercial Airplane Group uses a highly computerized Flight Test system. Everything from test planning to equipment control is handled through a large mainframe computer. This paper is an introduction to the structures which are necessary to efficiently run tests on many different airplanes at the same time, with a wide range of test requirements. This paper discusses the data bases required, the test planning and the procedures used to run a flight test program. Some data bases are common to all test programs while others are specific to a particular test program. The test planning begins with the Instrumentation Requirements estimating process. Then comes selecting parameters from the common data bases and marking them as required for a particular test program. New parameters are added to the common data bases as required. Once the process of identifying parameters to be recorded is started, the computer automatically generates airplane specific data bases and loads the information from the common data bases into them so that the other groups can select the specific instrumentation to be used to measure each parameter. As this planning is accomplished, information is added to the data bases so that they become more complete as the actual testing approaches, When the airplane enters it's testing phase, the data from these data bases is retrieved and provided to both the on-board data monitor system and the ground station to allow data to be acquired from the data acquisition system or from tape for data processing. As the testing is accomplished the computer data is updated to indicate the progress of the testing.

Within the Aerospace industry, the operational community is facing staff reductions, reduced skill levels, and greater complexity of space assets and space missions. This combination requires that techniques be developed that more efficiently interface a human operator with a complex computer system. Operational support of complex space systems will be greatly facilitated by better presentation of information. The presentation and distribution of complex data must evolve towards formats that are easily and naturally embraced by our sensory systems. Some of the information technologies/techniques that facilitate the presentation of complex dynamic graphical data fall into a category called integrated media. The cost of implementing integrated media (IM) architectures has decreased substantially within in the past five years. While implementation costs continue to recede, the quality and value of information that can be presented using IM technologies continues to improve. Today's IM architect can select a variety of components including digital interactive video, 3D Navigable Worlds, Multimedia Authoring Systems, standardized compressors for IM data, low cost high volume storage systems, and operating system extensions for temporal data management. Together, these components form a solid foundation for the development of a variety of compelling IM architectures. Existing satellite support and mission data processing architectures typically present tabular data for assessment. Some "advanced" systems include 2D graphical projections of the data. System experts are generally trained to correlate relationships between tabular data items. The training required to "learn" these complex relationships is tedious and time consuming. This complexity impedes productivity and as space systems increase in sophistication, these techniques for data assessment are quickly becoming antiquated. The development of a prototype decision support system explores the utility of an integrated media documentation system as part of a full-featured decision support architecture for satellite operations.

The MicroDAS-1000 is an airborne Data Acquisition System (DAS) designed to meet the growing needs of airframe manufacturers for extensive test data accumulation, processing and evaluation. As such, the system has been designed with emphasis on modularity, miniaturization and ease of operator usage and expansion. The MicroDAS product line includes a series of components used as building blocks to configure systems of virtually any size. The modular design of these components allows considerable latitude to the instrumentation engineer in configuring systems for simple or complex applications. The modular concept has been extended to the design of plug-in modules for different functional requirements and system applications. All units are under software control to allow rapid reconfiguration and setup as requirements for instrumentation and data gathering change.

The GPS Satellite System provides precise determination of time, space, and position of aerospace (airborne) vehicles during flight and flight test situations. The cost of "GPS" equipment has been decreasing dramatically -- a phenomenon similar to that which was experienced with "hand held" calculators 20 years or so ago. By the use of a multigain (and beam) antenna and GPS, a very low cost single axis system can be utilized for reception of telemetry and at the same time to provide accurate position, velocity, and acceleration information concerning the airborne vehicle.

Veda Systems Incorporated has recently completed the development of a completely open architecture, UNIX-based software environment for standard telemetry and more generic data acquisition applications. The new software environment operates on many state-of-the-art high-end workstations and provides a workstation independent, multiuse platform for front-end system configuration, database management, real-time graphic data display and data, logging.

This paper addresses the distributed systems implementation techniques used in the development of the EMR O/S90 Open Systems Telemetry System. Specifically, it presents the integration, networked load-balancing, and remote control aspects of the telemetry system which allow it to adapt to differing configurations and availability of resources.

The Global Positioning System has achieved a maturity whereby a large marketplace of users have developed. This marketplace has been flooded with many types of receivers from a large number of manufacturers. The broad acceptance of the system among military as well as commercial users has created this market, and receiver availability due to planned mass production has precipitated substantial price reduction for GPS receivers. OEM receivers are presently available on the market at such a low cost that their incorporation into flight test systems should be seriously considered. The data produced by the system has a reasonable and usable accuracy for platform position, flight vectors and time. These are suitable in most range applications and can either augment or replace present tracking methods such as multilateration or triangulation for vehicle position. The advantages of eliminating the need for tracking functions in ground control stations are obvious especially in multi-vehicle operations such as in air-to-air weaponry testing and range training missions. The simplification of operation in position determination becomes especially desirable for over-the-horizon platforms. In this case, ground or airborne relays must be employed which complicates the location task by orders of magnitude.

In this paper we describe the flight software for the SETS (Shuttle Electrodynamic Tethered System) experiment. The SETS experiment will fly as part of the TSS-1 (Tethered Satellite System) experiment on STS-46 currently scheduled for July 1992. The software consists of two major components: the SETSOS (SETS Operating System) and the SETS Application. The SETSOS is a UNIX-like operating system developed especially for realtime data acquisition, instrument control and command processing. The SETSOS, like all operating systems, provides resource management for application programs. It is UNIX-like in that access to resources is provided through a standard set of UNIX system calls. The SETSOS also implements the standard UNIX I/O model and a hierarchical file system. In addition to providing access to physical devices, the SETSOS provides support for two virtual devices: a packet-based data device and a command device. The packet-based data device is used by applications to place data into the telemetry stream. The command device is used to manage commands from the command uplink as well as other sources including other applications and other processors. The SETS Application is the primary program which runs under the SETSOS to handle data acquisition, instrument control and command processing. It executes as 5 separate processes, each performing a special task. The tasks include housekeeping data acquisition, limit checking, timeline management, and command processing. The processes communicate via shared memory. Time critical processing is coordinated by using signals and interrupts. In addition to a description of the software, we will discuss the relative merits and tradeoffs of using such a system design for command processing and data acquisition.

This paper describes a multiplexer-demultiplexer for high speed digital recorders. The multiplexer-demultiplexer enables a single-channel recorder (for example, MIL-STD-2179 recorders) to be used with up to eight asynchronous data channels, each channel being analog or digital. Time correlation between the different channels is preserved. The multiplexer and the demultiplexer are modular products and can be used under different environments (ships, aircraft, laboratory, ...).

In a PCM/FM+FM/FM system, the PCM data is added to the subcarriers at baseband and the composite signal is modulated onto the carrier. When the subcarrier messages are demodulated, part of the PCM signal's spectrum falls within the bandwidth of the subcarrier bandpass filters. This causes interference with the subcarrier messages, particularly those of the lower subcarrier frequencies. When designing a PCM/FM+FM/FM system, one is concerned with the placement of the subcarrier frequencies and the interference suffered by the subcarriers due to the PCM signal. This paper develops a relationship between the lowest frequency subcarrier, PCM bit rate and the resulting interference. The design procedure allows a bit rate or lowest frequency subcarrier to be selected for a specified interference ratio. The expression of the ratio is a complex integral which is reduced to a simple equation involving the system parameters.

This paper describes a biotelemetric application whereby information of tooth contact pressure from within the mouth of a human subject is transmitted to a bedside receiver where it is processed and used in the biofeedback treatment of nocturnal bruxism (grinding of the teeth). Bruxing information is encoded on a pulse width modulated 313 MHZ carrier. Issues that are addressed include miniaturization of the transmitter, minimization of power requirements, stabilization of carrier frequency, receiver selection, and the various problems associated with getting a radio frequency signal out of the mouth.

The ionosphere is a critical link in the earth's environment for space-based navigation, communications and surveillance systems. Signals sent down by the GPS satellites can provide an excellent means of studying the complex physical and chemical processes that take place there. GPS uses two frequencies to ascertain signal delays passing through the ionosphere. These are measured as errors and used to correct position solutions. Since this process is a means of measuring columns of Total Electron Content (TEC), multiple top-soundings from the GPS constellation could provide significant detail of the ionospheric pattern and possibly lead to enhancement of predictions for selectable areas and sites. This paper addresses transforming the GPS propagation delays (errors) into TEC and providing TEC contours on a PC-style workstation in real and integrated time and discusses a worldwide ionospheric network monitoring system.

A new antenna design, which is particularly suited for balloon telemetry applications, is presented. In the past, simple monopoles have been utilized as transmit antennas on balloon payloads. The monopole radiation pattern has an inherent null along its axis. This causes an undesirable loss of signal when the balloon is directly overhead. To prevent this occurrence, a microstrip antenna patch was incorporated into the monopole design. This combination, a "monopatch" antenna, provides sufficient coverage even when the balloon is directly over the ground station. The monopatch has been successfully flown on high altitude balloon flights.

The more sophisticated weapons systems become, the more information is required for thorough system test and evaluation. With the increasing capability in instrumentation technology, more data is being generated, and this in turn is stressing the amount of telemetry bandwidth available. In the training community this is even more serious because of the extremely large training areas and number of players involved. Total data bandwidth required becomes an insurmountable problem. When examining the telemetry data requirements for each application, we must constantly remember that information transfer is the key, not necessarily the transfer of large amounts of data. This problem can be solved by applying instrumentation techniques that enable significant information transfer without requiring excessive data bandwidth of the telemetry system. The general approach to the solution of this problem has been applied to the U.S. Government's SDI Program. Here the total system is modeled in a computer, and a complete test exercise can be simulated. Only significant information from the vehicle under test is telemetered periodically to verify the simulation. Another approach has been postulated by the U.S. Defense Advanced Research Projects Agency (DARPA) in their SIMNET studies. Here an exercise is simulated both on the ground and in the test vehicle, and information is transmitted from the test vehicle only when the actual vehicle performance differs from the simulation. By using techniques of this type, savings of a factor of 10 or more can be experienced in the required telemetry bandwidth. This paper examines various techniques that can be used to minimize required telemetry bandwidth.

An improved ionospheric delay correction model for a transionospheric electromagnetic pulse (EMP) is used for estimating the total-electron-content (TEC) profile of the path and accurate ranging of the EMP source. For a known pair of time of arrival (TOA) measurements at two frequency channels, the ionospheric TEC information is estimated using a simple numerical technique. This TEC information is then used for computing ionospheric group delay and pulse broadening effect correction to determine the free space range. The model prediction is compared with the experimental test results. The study results show that the model predictions are in good agreement with the test results.

One of the problems in analyzing data is getting the data to the analysis system. The data can be stored in a variety of ways, from simple disk and tape files to a sophisticated relational database system. The variety of storage techniques requires the data analysis system to be aware of the details of how the data may be accessed (e.g., file formats, SQL statements, BBN/Probe commands, etc.). The problem is much worse in a network of heterogeneous machines; besides the details of each storage method, the analysis system must handle the details of network access, and may have to translate data from one vendor format to another as it moves from machine to machine. This paper describes a simple and powerful software interface to telemetry data in a distributed heterogeneous networking environment, and how that interface is being used in a diagnostic expert system. In this case, the interface connects the expert system, running on a Sun UNIX machine, with the data on a VAX/VMS machine. The interface exists as a small subroutine library that can be linked into a variety of data analysis systems. The interface insulates the expert system from all details of data access, providing transparent access to data across the network. A further benefit of this approach is that the data source itself can be a sophisticated data analysis system that may perform some processing of the data, again transparently to the user of the interface. The interface subroutine library can be readily applied to a wide variety of data analysis applications.

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